Novel coumarin fluorescent dyes: Synthesis, structural characterization and recognition behavior towards Cu(II) and Ni(II)

A series of novel coumarin dyes (3-12) were designed and synthesized. The structures of the dyes were characterized by IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, MS and single crystal X-ray diffraction. 3-(2-Benzoylhydrazonotrifluoroethyl)-7-(N,N-diethylamino)coumarin (11) could recognize Cu²⁺ and Ni²⁺ selectively in aqueous solution. Upon addition of Cu²⁺ or Ni²⁺ to 11 a blue shift or a bathochromatic shift of the absorption band was observed while the emission band blue-shifted with decrease in the fluorescence intensity. Upon addition of Cu²⁺ the color of the solution of 11 changed from orange to red. The results showed that 11 could be used as an optical chemosensor of Cu²⁺ and Ni²⁺.     

In situ Cu(II)-containing chiral polymer complex sensor for enantioselective recognition of phenylglycinol

A chiral polymer P1 was synthesized by the polymerization of 2,5-dibutoxy-1,4-di(benzaldehyde)-1,4-diethynylbenzene (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via Schiff's base formation, and the chiral polymer P2 could be obtained by the reduction reaction of P1 with NaBH₄. P2 can serve as a “turn-off” fluorescent sensor toward Cu²⁺ and Ni²⁺. The in situ generated Cu(II)-containing polymer complex of P2 (Cu(II)-P2) can exhibit remarkable “turn-on” fluorescence enhancement response and considerable enantioselectivity toward unmodified phenylglycinol via a ligand displacement mechanism. More importantly, (R,R)-Cu(II)-P2 solution can turn on bright blue fluorescence color change again upon addition of l-phenylglycinol under a commercially available UV lamp, which can be clearly observed by the naked eyes for direct visual discrimination at low concentration. The simple, rapid and sensitive benign process makes this protocol promising for recognition of phenylglycinol enantiomers.     

A highly selective fluorescent sensor for Hg based on the water-soluble poly(p-phenyleneethynylene)

The conjugated polymer P-1 could be synthesized by the polymerization of 4,7-diethynyl-benzo[2,1,3]thiadiazole (M-1) and 1,4-bis[3′-(N,N-diethylamino)-1′-oxapropyl]-2,5-diiodobenzene (M-2) via Pd-catalyzed Sonogashira reaction. The water-soluble conjugated polyelectrolyte P-2 could be obtained by the reaction of P-1 with ethyl bromide. Both P-1 and P-2 can emit orange fluorescence. The responsive optical properties of P-1 and P-2 on Hg²⁺ were investigated by fluorescence spectra. Hg²⁺ can lead to nearly complete fluorescence quenching of P-1. On the contrary, Hg²⁺ can show the most pronounced fluorescence enhancement response of P-2 in aqueous solution without interference from those coexistent ions, such as K⁺, Mg²⁺, Pb²⁺, Co²⁺, Ni²⁺, Ag⁺, Cd²⁺, Cu²⁺, Fe³⁺ and Zn²⁺. The results also exhibit that this kind of water-soluble conjugated polyelectrolyte can be used as a highly sensitive and selective fluorescence sensor for Hg²⁺ detection in water.     

Electrochemical behaviour of tetraazamacrocyclic nickel(II) complexes functionalized with crown ethers

Tetraazamacrocyclic nickel(II) complexes linked by the system of conjugated double bonds with one or two benzo-15-crown-5 moieties (2Ni and 3Ni) were synthesized and characterized. The CV of these complexes in acetonitrile (ACN) solution exhibited reversible Ni^II/III redox process. At more positive potentials oxidation of the bezno-15-crown-5 ether (B15C5) moiety was found. In complexes 2Ni and 3Ni redox potential of Ni^II/III did not change after the interactions of alkali and alkaline earth metal cations with B15C5 unit. However, the presence of guest cations caused a significant change of B15C5 oxidation potential. Complexation of two Cl⁻ anions to the coordinated Ni^II in 2Ni and 3Ni resulted in an appreciable shift of both Ni^II/III and B15C5 redox processes after addition of metal cations. Behaviour of complexes 2Ni and 3Ni was compared with behaviour of similar Cu^II complexes.     

Optical properties and aggregation of novel azo-dyes bearing an end-capped oligo(ethylene glycol) side chain in solution,solid state and Langmuir–Blodgett films

Optical properties and aggregation of two novel azo-dyes N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl]phenyl}-N-(3,6,9-trioxadecas-1-yl)amine (RED-PEGM-3) and N-methyl-N-{4-[(E)-(4-nitrophenyl)diazenyl] phenyl}-N-(3,6,9,12,15,18,21,24-octaoxapentaeicos-1-yl)amine (RED-PEGM-8) were studied by UV–vis spectroscopy in solution, solid state and Langmuir–Blodgett films. The results were compared to those obtained for their precursor 1-amino-4′-nitroazobenzene (Disperse Orange 3, DO3) and 1-N-methylamino-4′-nitroazobenzene (RED-H). Increasing the polarity of methanol:water mixtures gave rise to the formation of H-aggregates for all dyes. Similar aggregates were also detected in cast films. NOESY, 2D ¹H NMR experiments carried out in aqueous solutions of RED-PEGM-8 revealed the formation of atypical antiparallel H-aggregates. Only RED-PEGM-3 gave traces of J-aggregates in the solid state. RED-PEGM-3 and RED-PEGM-8 readily form J-aggregates in Y-type Langmuir–Blodgett films.     

Reactions of bis(3-aminopropyl)amine with formaldehyde in the presence of a metal ion: Preparation of a metal-free macropolycycle and a dinuclear copper(II) complex

The reaction of bis(3-aminopropyl)amine with excess formaldehyde in the presence of Ni²⁺ ion produces the macropentacyclic compound L¹(ClO₄)₂ (1) L¹ = 1,3,7,11,13,17- hexaazapentacyclo[15.3.1.1^3.7.1^7.13.1^13.17]tetracosane). The dinuclear complex [Cu₂(L²)₂(H₂O)₂](ClO₄)₂ (2) (HL¹ = 1-(3-aminopropyl)-3-(hydroxymethyl)-1,3-diazacyclohexane) as well as 1 can be prepared by the condensation reaction in the presence of Cu²⁺ ion. Interestingly, 2 · 2H₂O exhibits uncommon magnetic behavior.     

Nickel(II)‐imprinted monolithic columns for selective nickel recognition

Ni²⁺‐imprinted monolithic column was prepared for the removal of nickel ions from aqueous solutions. N‐Methacryloyl‐L ‐histidine was used as a complexing monomer for Ni²⁺ ions in the preparation of the Ni²⁺‐imprinted monolithic column. The Ni²⁺‐imprinted poly(hydroxyethyl methacrylate‐N‐methacryloyl‐L ‐histidine) (PHEMAH) monolithic column was synthesized by bulk polymerization. The template ion (Ni²⁺) was removed with a 4‐(2‐pyridylazo) resorcinol (PAR):NH₃? NH₄Cl solution. The water‐uptake ratio of the PHEMAH–Ni²⁺ monolith increased compared with PHEMAH because of the formation of nickel‐ion cavities in the polymer structure. The adsorption of Ni²⁺ ions on both the PHEMAH–Ni²⁺ and PHEMAH monoliths were studied. The maximum adsorption capacity was 0.211 mg/g for the PHEMAH–Ni²⁺ monolith. Fe³⁺, Cu²⁺, and Zn²⁺ ions were used as competitive species in the selectivity experiments. The PHEMAH–Ni²⁺ monolithic column was 268.8, 25.5, and 10.4 times more selective than the PHEMAH monolithic column for the Zn²⁺, Cu²⁺, and Fe³⁺ ions, respectively. The PHEMAH–Ni²⁺ monolithic column could be used repeatedly without a decrease in the Ni²⁺ adsorption capacity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Conversion of soybean oil into ion exchange resins: Removal of copper (II), nickel (II), and cobalt (II) ions from dilute aqueous solution using carboxylate‐containing resin

An ion‐exchange resin containing carboxylic acid groups was prepared by reaction of epoxidized soybean oil with triethylene tetramine, followed by hydrolysis of glycerides by using sodium hydroxide solution. The cation exchange capacity of the resins was determined to be 3.50 mequiv/g. The adsorption capacity for Cu²⁺, Ni²⁺, and Co²⁺ on the obtained resin at pH 5.0 was found to be 192, 96, and 78 mg/g, respectively. Effect of pH on the adsorption capacity for copper (II), nickel (II), and cobalt (II) ions were also studied. Cu²⁺, Ni²⁺, and Co²⁺ were adsorbed at a pH above 3. These metal ions adsorbed on the resin are easily eluted by using 1N HCl solution. The selectivity of the resin for Cu²⁺ from mixtures containing Cu²⁺/Co²⁺/Ni²⁺ ions in the presence of sodium chloride was also investigated © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2386–2396, 2002     

A new copper(II) selective fluorescence probe based on naphthalimide: Synthesis,mechanism and application in living cells

A new fluorescence probe L based on naphthalimide has been synthesized for selective and quantitative detection of Cu^2 + in CH₃CN:H₂O (4:1, v/v) solution. L exhibited a strong green fluorescence. Upon addition of 2 equiv. of Cu^2 +, the fluorescence emission shows a steady and smooth decrease until a plateau is reached with a 30-fold quenching of fluorescence intensity. In the presence of Cu^2 +, the absorbance peak of L maximum at 466 nm decreased, and a new absorption band at 600 nm appeared. Under the identical conditions, other physiological and environmental important metal ions induced negligible spectroscopic changes. The 1:2 stoichiometry binding mode of L with Cu^2 + was supported by the Benesi–Hildebrand analysis and ESI-MS spectra studies. The detection limit for Cu^2 + was estimated to be 64 ppb. Fluorescence microscopy experiments showed that L has practical application in living cells.     

In situ synthesis and dielectric properties of copper(II) and nickel(II) chiral Schiff base complexes

Two chiral Schiff base-containing complexes, [Cu(L¹)](ClO₄)₂·H₂O (1, L¹ = (S,S)-N1,N2-bis((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) and [Ni(L²)₂](ClO₄)₂ (2, L² = (S,S)-N1-((1H-imidazol-4-yl)methylene)cyclohexane-1,2-diamine) were synthesized from the reaction mixture of 1H-imidazole-4-carbaldehyde, (S,S)-1,2-diaminocyclohexane and Cu(ClO₄)₂·6H₂O or Ni(ClO₄)₂·6H₂O in methanol. Single-crystal X-ray diffraction analyses reveal that the in situ generated chiral Schiff base ligands L¹ and L² are bisubstituted and monosubstituted, respectively, corresponding to the different metal ions Cu^II and Ni^II. Variable-frequency and -temperature dielectric properties of 1 and 2 have been studied.     

Cationic conjugated polyelectrolyte-based fluorometric detection of copper(II) ions in aqueous solution

A series of water-soluble cationic polyfluorene copolymer containing 2,2′-bipyridine moieties (PFP-P_1-3) in the backbone were designed and synthesized as the fluorescent probes for Cu²⁺ ions. In the absence of the Cu²⁺ ion, the PFP-P₂ exhibits strong fluorescence emission in aqueous solution. Upon adding the Cu²⁺ ion, the PFP-P₂ coordinates to Cu²⁺ ions through weak N?Cu interactions, and its fluorescence is efficiently quenched by the Cu²⁺ ion with a Stern-Volmer constant (K_sv) of 1.44 × 10⁷ M⁻¹. The new method has high sensitivity with a detection limit of 20 nM. The minor interference from other heavy metal ions clearly shows that the PFP-P₂ can be used as the Cu²⁺ ion probe with good selectivity.     

Syntheses and structures of a phenoxo-bridged copper(II) distorted cubane and related complexes with 2-hydroxy-N-(2-pyridylalkyl)benzamide ligands

Two new pyridylalkylamide ligands containing phenol groups appended to the amide, 2-hydroxy-N-(2-pyridylmethyl)benzamide (HL^PhOH) and 2-hydroxy-N-(2-pyridylethyl)benzamide (HL^PhOH′), were synthesized. Copper(II) complexes of these ligands were synthesized and characterized by X-ray crystallography, ESI-MS, FTIR, UV/Vis, and EPR spectroscopy. When basic Et₃N was used to deprotonate the ligands, tetracopper(II) [Cu₄(L^PhO)₄] (1) or dicopper(II) [Cu₂(L^PhO′)₂(CH₃OH)₂] (3) were formed. When base was not used, mononuclear [Cu(HL^PhOH)₂Cl₂] (2) resulted. Complex 1 possesses a distorted cubane-like structure, with the ligands bridging via the phenoxo oxygen atoms, and the copper atoms possessing a distorted square planar geometry. The ligands in dimeric complex 3 also bridge between copper(II) atoms via the phenoxo oxygen atoms, and the copper atoms are square pyramidal. Monomeric 2 is a tetragonally distorted six-coordinate species with pyridyl N atoms and chloride ligands in the equatorial plane, and long interactions with the amide carbonyl O atoms in the axial positions.     

Synthesis,characterization and spectroscopic properties of some new azo disperse dyes derived from 4-hydroxybenzo[h]quinolin-2-(1H)-one as a new synthesized enol type coupling component

4-Hydroxybenzo[h]quinolin-2-(1H)-one (IV) was synthesized from the cyclocondensation of 3-(naphthalen-1-ylamino)-3-oxopropanoic acid (I) or N,N′-di(naphthalen-1-yl)malonamide (II) and subsequently coupled with diazotized p-substituted aniline derivatives. The structures of the synthesized dyes were determined by spectroscopic and analytical methods. Solvent effects on the ultraviolet–visible absorption spectra of these novel azo dyes were studied in six pure organic solvents with different polarities. The color of the dyes is discussed with respect to the nature of substituents on the benzene ring. The tautomeric structures of the azo compounds were studied by ¹H NMR spectroscopy in DMSO-d₆ and CDCl₃. The effects of acid and base on the visible absorption spectra of the dyes were also reported. Ionization constants, pK_a, for these dyes were determined in 80 vol. % ethanol–water medium at room temperature and correlated with the substituent constant, σ_p.     

A new selective fluorescent chemosensor for Cu(II) ion based on zinc porphyrin-dipyridylamino

A new fluorescent chemosensor 5-(p-N,N′-bis(2-pyridyl)amino)phenyl-10,15,20-tris(p-methoxyphenyl)porphyrin zinc has been designed and synthesized by the Ullmann-type coupling. It displays high selectivity for Cu²⁺ ion and exhibits fluorescence quenching upon binding of Cu²⁺ ion with an “on–off” type fluoroionophoric switching property, and its fluorescence can be revived by addition of EDTA disodium solution.     

Copper(II) complexes derived from bidentate N,O-ligands for catalytic aerobic oxidation

Two Cu^II complexes based on bidentate N,O-ligands have been synthesized and structurally characterized. X-ray structural analysis revealed that in complex 1 the Cu^II center adopts an unusual near tetrahedral coordination geometry, while the Cu^II core in 2 is traditionally square planar, albeit both of them have a N₂O₂ coordination environment and two compounds are mononuclear bis-ligand neutral complexes. A two-dimensional sheet-like network was observed in 2, resulting from the weak Cu…O contacts between the nitrato groups and axial Cu^II sites. Both complexes were tested for catalytic aerobic oxidation of benzylic alcohol and the results indicated that 2 was a better catalyst than 1. High yield of benzaldehyde was observed when using 2 as a catalyst in combination with TEMPO in an aqueous potassium carbonate solution at 60 °C.     

A ratiometric fluorescent sensor for zinc(II) with high selectivity

Spectroscopic studies revealed that the compound [N,N′-di(quinoline-2-methylene) -1,2-phenylenediimine] (1) exhibited a rather high selectivity toward Zn²⁺ over other metal ions, even Cd²⁺. In acetonitrile, the red shift of fluorescent emission from 396 nm to 426 nm upon zinc binding is due to the formation of a 1:1 metal/ligand complex.     

The first crystallographically-characterised Cu(II) xanthate

The copper(II) xanthate Cu(S₂COEt)₂·TMEDA (1) (TMEDA = N,N-tetramethylethylenediamine) has been synthesised and is the first structurally-characterised xanthate of copper in the + 2 oxidation state. 1 has an octahedral cis, cis, cis-ligand arrangement about the metal, in which xanthate chelation is markedly asymmetric. Both bulk thermal decomposition and film growth by aerosol-assisted chemical vapour deposition (AACVD) using 1 as precursor lead to the formation of Cu₂S.     

Novel 4-(2,2,6,6-tetramethylpiperidin-4-ylamino)-1,8-naphthalimide based yellow-green emitting fluorescence sensors for transition metal ions and protons

Two novel yellow-green emitting 1,8-naphthalimides, containing a 4-amino-2,2,6,6-tetramethylpiperidinyl moiety, were configured as “fluorophore–spacer–receptor” systems. The photophysical characteristics of the dyes were investigated in both DMF and water/DMF (4:1, v/v) solutions. The ability of the new compounds to detect cations was evaluated by means of the changes in their fluorescence intensity imparted by the presence of transition metal ions (Cu²⁺, Pb²⁺, Zn²⁺, Ni²⁺) and protons. The presence of metal ions and protons was found to disallow photoinduced electron transfer resulting in enhanced fluorescence intensity. The results clearly show that only Cu²⁺ ions and protons were effectively detected, indicating the potential of the novel compounds as highly efficient “off–on” switchers for Cu²⁺ ions and protons.     

Chromogenic sensing of Cu(II) by imino linked thiacalix[4]arene in mixed aqueous environment

Thiacalix[4]arene based imino receptors 4–5 carrying azophenol appendage have been synthesized and studied for their binding abilities towards different metal ions (Li⁺, Na⁺, K⁺, Cd²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Ag⁺, Pb²⁺ and Hg²⁺). Receptor 4 showed selective chromogenic sensing for Cu²⁺ ions in mixed aqueous conditions (THF:H₂O, 9:1 v/v).     

Alkoxo- and carboxylato-bridged hexanuclear copper(II) complex: Synthesis,structure and magnetic properties

Reaction of copper(II) nitrate trihydrate with N,N-dimethylethanolamine (dmea) and pivalic acid in methanol led to the hexanuclear copper(II) complex Cu₆(η¹:μ₂-C₄H₁₀NO)₄(η¹:η¹:μ₂-C₅H₉O₂)₄(η¹:μ₁-C₅H₉O₂)₂(μ₃-OH)₂ (1). The crystal structure of 1 indicates that hexametallic centers are bridged by the μ₃-alkoxo, dmea oxygens, and the μ₂-dicarboxylato oxygen atoms of pivalate ions. Furthermore, in the asymmetric unit, three types of copper ions have been found labeled as Cu₁, Cu₂ and Cu₃. The Cu₂ takes a distorted octahedral shape, whereas Cu₁ and Cu₃ adopt square pyramidal geometries. The complex 1 shows strong antiferromagnetic interactions through the oxo groups within the dimeric units (J = − 82.6 to − 25.8 cm^− 1) and weak antiferromagnetic couplings between the dimers (J = − 10.9 and 0.8 cm^− 1).